The present application relates to spinal instrumentation systems, more particularly to spacer assemblies for use in interbody fusion procedures of the spine. Most particularly, the present invention relates to end caps for use with spacers that are used in spinal surgeries.
There has been a gradual acceptance of interbody fusion as a procedure for a number of spinal disorders. Interbody fusion procedures employ the use of surgical mesh tubes, see for example "Chapter 10: Titanium Surgical Mesh for Vertebral Defect Replacement and Intervertebral Spacers", Gary L. Lowery and Jurgen Harms, Manual of Internal Fixation of the Spine, edited by John S. Thalgott and Max Aebi, Lippincoll-Raven Publishers, Philadelphia, 1996, which is incorporated herein by reference. The surgical mesh tubes are used to reinforce weak, bony tissues in orthopaedic procedures and they act as a structural support for the spine. Moreover, a mesh pattern in the conventional surgical mesh tubes provides access for bone to grow and fuse within the tube. These surgical mesh tubes are often formed of titanium and are available in varying shapes and sizes. In addition, surgical mesh tubes can be trimmed on site by the surgeon to better provide an individual fit for each patient.
Internal rings, connector screws, and fenestrated end plates have been added to the surgical mesh tube. See, for example, "Titanium Surgical Mesh for Vertebral Defect Replacement and Intervertebral Spacers", Gary L. Lowery and Jurgen Harms, Manual of Internal Fixation of the Spine, edited by John S. Thalgott and Max Aebi, Lippincoll-Raven Publishers, Philadelphia, 1996. As discussed in the before mentioned article, conventional rings attach to the contoured mesh through the use of screws. The conventional rings strengthen the surgical mesh tube by acting as a reinforcement to aide in better distributing the axial loads previously taken wholly by the edge of the surgical mesh tube.
According to the present invention a spacer assembly is provided for use in spinal surgeries. The spacer assembly comprises a spacer having opposite ends and a side wall extending between the opposite ends and at least one end cap coupled to at least one of the opposite ends of the spacer. Each end cap includes an inner end facing the spacer, an outer end, and a side wall extending between the inner and outer ends. The side wall of the end cap is formed for engagement with the side wall of the spacer to couple the end cap and spacer together.
In preferred embodiments, the spacer includes a passageway between the opposite ends and the inner end of the end cap extends into the passageway. The side wall of the end cap converges from the outer end toward the inner end to wedge fit the end cap in the spacer. In addition, the end cap includes at least one projection coupled to the side wall and formed to engage the spacer. The projection blocks sliding movement of the end cap in the passageway of the spacer. Also, the outer end includes an outer surface that promotes bone ingrowth, such as for example a porous coating or a serrated surface. Preferably, the engagement of the end cap side wall and the projection with the side wall of the spacer 12 provides the sole mechanical connection between the end cap and the spacer.
Alternatively, the side wall of the end cap is formed to include a slot extending between the outer and inner ends. The slot allows the side wall of the end cap to be compressed as it is inserted into the passageway of the spacer. Once positioned in the passageway, the side wall expands toward the side wall of the spacer to friction lock the end cap in the passageway of the spacer. At least one projection extends from the side wall of the compressible end cap for engagement with the spacer to block sliding movement of the end cap in the passageway.
Still further, the side wall of the spacer includes an outer surface and an alternative end cap is formed to extend over the opposite end of spacer and be coupled to the outer surface. The end cap includes an outer end, an inner end, and a side wall that extends between the outer and inner ends. In addition, the side wall includes a slot extending between the outer and inner ends. The slot allows the side wall of the end cap to be expanded as it is placed about the end of the spacer. Once positioned about the outer surface of the spacer, the side wall of the end cap contracts toward the side wall of the spacer to friction lock the end cap on the side wall of the spacer. At least one projection extends from the side wall of the compressible end cap for engagement with the spacer to block sliding movement of the end cap in the passageway.
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.